Rotary pumps of the meshing gear type are well known for desired, volumetric pumping. They comprise a pair of meshing gears in a housing, so that the rotating gears pump fluid around their outer peripheries transversely across the gears, while pumping little or no fluid back in the other direction through the meshing gears. The term "gear" is intended to include any rotary structure having projections or teeth which meet with other projections of another rotary member to provide gear pump-like action.
In Garland U.S. Pat. No. 3,986,801 a gear-type rotary pump is shown in which the gear teeth are helically arranged on the gear and mesh with similarly helically arranged teeth on a second gear. In such a circumstance, a gear pump is provided which can pump fluids from end to end of the gear rather than transversely across the gear. However, upon analysis of the disclosure of the Garland patent, it becomes apparent that the pump exhibits a substantial amount of back leakage so that its operation is rather inefficient and non-volumetric. One reason for this comes from the fact that the helically arranged teeth of the pump disclosed in the Garland patent exhibit an overall degree of wrap within a range of 120 degrees to 270 degrees. This degree of wrap is the circumferential angle that each helical tooth passes through as it extends from one end to the other end of its gear.
Because of such a high degree of wrap, the helical gears, and the channels between them, cross and recross each other frequently, creating a labyrinth of connected, crossing spaces, which provide rearward "escape hatches" for fluid being pumped by the Garland device. Therefore, the pumping of the Garland device is rather inefficient.
Also in the Garland device there is no creation of completely closed channels defined completely between the engaged, rotating gears with their helically arranged teeth. Thus, the Garland device exhibits further disadvantages at ultra high pressures, since the outer casing which holds the rotating gears is always a part of the formed chambers that attempt to compress and pump fluids through the Garland device.
In accordance with this invention, an improved helical, toothed rotary pump is provided, which exhibits substantially less back leakage than the Garland-type pump, and which, in preferred embodiments, is capable of forming movable pumping chambers between intersecting helical teeth of the engaging gears, which chambers are entirely enclosed between the engaging teeth and essentially out of contact with the casing which surrounds the teeth. Thus, the pump of this invention, while usable for pumping liquids, gases, and creating vacuums, is particularly suitable for ultra high pressure pumping of gases or the like, since the casing of the pump does not have to be reinforced to withstand the ultra high pressures that can be generated in fluids passing through the pump of this invention, nor is the clearance between the case and the teeth subject to the ultra high pressure, with consequent leakage.
Additionally, the pump of this invention may be manufactured at lower cost and greater simplicity than the pump of Garland. The pump of this invention may be used as the basis for a new internal combustion engine, because of its capacity for ultra high compression, coupled with smooth, continuous operation and low back-leakage.
The pump of this invention operates by the creation, between helical teeth of opposite, meshing gears, a continuing series of chambers for fluid which are defined at the inlet end of the pump and travel down the gears in a helical path to the outlet end. Thus, fluid contained in the chambers is forcefully driven from the inlet end to the outlet end, with compression if the pump is operated in one direction, and with expansion if the pump is operated in the other direction of rotation, as in the situation where the pump is being used as an internal combustion engine. The pump exhibits low back leakage, resulting from an inherent, good sealing of the chambers that are continuously formed as the pump rotates.